Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.42	11.349%	$102.9087	$102.91	$102.90	$102.90
Purchase #2	$64.84	3.824%	$67.3195	$67.32	$67.30	$67.30
Purchase #3	$116.90	6.806%	$124.8562	$124.86	$124.85	$124.90
Purchase #4	$145.28	9.397%	$158.932	$158.93	$158.95	$158.90
Purchase #5	$217.41	11.612%	$242.6556	$242.66	$242.65	$242.70
Purchase #6	$87.50	12.361%	$98.3159	$98.32	$98.30	$98.30
Purchase #7	$237.95	5.334%	$250.6423	$250.64	$250.65	$250.60
7 purchase totals =	$962.30		$1,045.6302	$1,045.64	$1,045.60	$1,045.60